Genomic landscape of intracranial meningiomas

Methylation profiling in the contemporary management of meningioma

BACKGROUND

The last decade has seen major international research efforts focus on better understanding disease heterogeneity in meningioma. Multiple molecular platforms have generated significant biological and clinical utility, and there is a need to translate these findings into routine clinical practice. Here we review the role of DNA methylation profiling in meningioma and advocate for its widespread adoption.

METHODS

We review modern DNA methylation-based classification and outcome prediction tools in meningioma. Biological classifiers, which were constructed agnostic to outcome using unsupervised approaches, outcome predictors, and liquid biopsy models are discussed in detail.

RESULTS

DNA methylation has been used for biological classification and outcome in meningioma with considerable success. Several groups have proposed novel molecular classification systems which share similar features with one another and outperform WHO grade in their ability to predict outcome and explain subgroup-specific biological processes. In addition, recent studies have suggested a role for methylation-based liquid-biopsy in meningioma, which represents an exciting avenue for further exploration.

CONCLUSIONS

DNA methylation profiling has been revolutionary in meningioma. There is a need for widespread adoption of these approaches to personalize care and inform clinical trial design.

Salvage Stereotactic Radiosurgery for Recurrent WHO Grade 2 and 3 Meningiomas: A Multicenter Study (STORM)

PURPOSE

The role of stereotactic radiosurgery (SRS) in the management of grade 2 and 3 meningiomas is not well elucidated. Unfortunately, local recurrence rates are high, and guidelines for management of recurrent disease are lacking. To address this knowledge gap, we conducted STORM (Salvage Stereotactic Radiosurgery for Recurrent WHO Grade 2 and 3 Meningiomas), a multicenter retrospective cohort study of patients treated with primary SRS for recurrent grade 2 and 3 meningiomas.

METHODS AND MATERIALS

Data on patients with recurrent grade 2 and 3 meningioma treated with SRS at first recurrence were retrospectively collected from 8 academic centers in the United States. Patients with multiple lesions at the time of initial diagnosis or more than 2 lesions at the time of first recurrence were excluded from this analysis. Patient demographics and treatment parameters were extracted at time of diagnosis, first recurrence, and second recurrence. Oncologic outcomes, including progression-free survival (PFS) and overall survival, as well as toxicity outcomes, were reported at the patient level.

RESULTS

From 2000 to 2022, 108 patients were identified (94% grade 2, 6.0% grade 3). A total of 106 patients (98%) had upfront surgical resection (60% gross-total resection) with 18% receiving adjuvant radiation therapy (RT). Median time to first progression was 2.5 years (IQR, 1.34-4.30). At first recurrence, patients were treated with single or fractionated SRS to a median marginal dose of 16 Gy to a maximum of 2 lesions (87% received single-fraction SRS). The median follow-up time after SRS was 2.6 years. The 1-, 2-, and 3-year PFS was 90%, 75%, and 57%, respectively, after treatment with SRS. The 1-, 2-, and 3-year overall survival was 97%, 94%, and 92%, respectively. In the multivariable analysis, grade 3 disease (HR, 6.80; 95% CI, 1.61-28.6), male gender (HR, 3.48; 95% CI, 1.47-8.26), and receipt of prior RT (HR, 2.69; 95% CI, 1.23-5.86) were associated with worse PFS. SRS dose and tumor volume were not correlated with progression. Treatment was well tolerated, with a 3.0% incidence of grade 2+ radiation necrosis.

CONCLUSIONS

This is the largest multicenter study to evaluate salvage SRS in recurrent grade 2 and 3 meningiomas. In this select cohort of patients with primarily grade 2 meningioma with a potentially more favorable natural history of delayed, localized first recurrence amenable to salvage SRS, local control rates and toxicity profiles were favorable, warranting further prospective validation.

Meningioma: International Consortium on Meningiomas consensus review on scientific advances and treatment paradigms for clinicians, researchers, and patients

Meningiomas are the most common primary intracranial tumors in adults and are increasing in incidence due to the aging population and increased access to neuroimaging. While most exhibit nonmalignant behavior, a subset of meningiomas are biologically aggressive and are associated with treatment resistance, resulting in significant neurologic morbidity and even mortality. In recent years, meaningful advances in our understanding of the biology of these tumors have led to the incorporation of molecular biomarkers into their grading and prognostication. However, unlike other central nervous system (CNS) tumors, a unified molecular taxonomy for meningiomas has not yet been established and remains an overarching goal of the Consortium to Inform Molecular and Practical Approaches to CNS Tumor Taxonomy-Not Official World Health Organization (cIMPACT-NOW) working group. Additionally, clinical equipoise still remains on how specific meningioma cases and patient populations should be optimally managed. To address these existing gaps, members of the International Consortium on Meningiomas including field-leading experts, have prepared this comprehensive consensus narrative review directed toward clinicians, researchers, and patients. Included in this manuscript are detailed overviews of proposed molecular classifications, novel biomarkers, contemporary treatment strategies, trials on systemic therapies, health-related quality-of-life studies, and management strategies for unique meningioma patient populations. In each section, we discuss the current state of knowledge as well as ongoing clinical and research challenges to road map future directions for further investigation.

Spatial Distribution of Meningiomas: A Magnetic Resonance Image Atlas

BACKGROUND AND OBJECTIVES

The size and anatomic location of meningiomas have been shown to correlate with distinct clinical manifestations, histopathological subtypes, and surgical risk. However, meningioma anatomic origin sites can be obscured in large tumors and those crossing compartments. We therefore sought to apply unbiased lesion mapping to localize intracranial meningioma distributions and their association with biology and grade.

METHODS

MRI scans, World Health Organization (WHO) grade, and a molecularly Integrated Grade (IG) derived from cytogenetics were analyzed from adult patients with intracranial meningiomas. Semi-automated tumor segmentation was performed on T1-weighted contrast-enhanced MRI. We used the voxel-based lesion mapping technique to generate a meningioma atlas, mapping spatial frequency and correlating with tumor grades.

RESULTS

Of 881 patients with meningioma (median age: 57 years, 68.8% female), 589 were WHO grade 1 (66.8%), 265 WHO grade 2 (30.1%), and 27 WHO grade 3 (3.1%) with a median tumor volume of 14.6 cm3. After molecular reclassification, 585 were IG-1 (66.4%), 160 IG-2 (18.2%), and 136 IG-3 (15.4%). Benign tumors were concentrated in and around the midline anterior skull base while malignant meningiomas were enriched in the falcine/parasagittal region and the sphenoid wing, similar to the distribution when stratified by chromosome 1p loss. Meningiomas exhibited sharper spatial clustering when stratified by the molecular IG than by WHO grade. WHO grade 2 meningiomas divided equally across IG 1-3, with corresponding partition of spatial distribution in the midline anterior skull base (in WHO grade 2, IG-1) and falcine/parasagittal and sphenoid regions (WHO grade 2, IG-3). Meningioma volumes significantly varied across age, sex, and WHO/IG grades.

CONCLUSION

We demonstrate the utility of voxel-based lesion mapping for intracranial tumors, characterizing distinct meningioma distribution patterns across histopathological and molecularly defined grades. Molecular grading associated with sharper tumor spatial clusters, supporting a phenotype-genotype association in meningiomas.

Single versus multiple reoperations for recurrent intracranial meningiomas

PURPOSE

To identify the risk factors and management of the multiple recurrences and reoperations for intracranial meningiomas.

METHODS

Data of a neurosurgical series of 35 patients reoperated on for recurrent intracranial meningiomas were reviewed. Analyzed factors include patient age and sex, tumor location, extent of resection, WHO grade, Ki67-MIB1 and PR expression at initial diagnosis, time to recurrence; pattern of regrowth, extent of resection, WHO grade and Ki67-MIB1 at first recurrence were also analyzed. All these factors were stratified into two groups based on single (Group A) and multiple reoperations (Group B).

RESULTS

Twenty-four patients (69%) belonged to group A and 11 (31%) to group B. The age < 65 years, male sex, incomplete resection at both initial surgery and first reoperation, and multicentric-diffuse pattern of regrowth at first recurrence are risk factors for multiple recurrences and reoperations. In group B, the WHO grade and Ki67-MIB1 increased in further recurrences in 54% and 64%, respectively. The time to recurrence was short in 7 cases (64%), whereas 4 patients (36%) further recurred after many years. Eight patients (73%) are still alive after 7 to 22 years and 2 to 4 reoperations.

CONCLUSION

The extent of resection and the multicentric-diffuse pattern of regrowth at first recurrence are the main risk factors for multiple recurrences and reoperations. Repeated reoperations might be considered even in patients with extensive recurrent tumors before the anaplastic transformation occurs. In such cases, even partial tumor resections followed by radiation therapy may allow long survival in good clinical conditions.

Neuroradiological features of patients with bilateral macronodular adrenocortical disease and meningiomas associated or not with genetic variants of ARMC5- a case series

INTRODUCTION

Meningiomas are the most common primary brain and central nervous system tumors, accounting for approximately 40% of these tumors. The most important exams for the radiological study of meningiomas are computed tomography (CT) and magnetic resonance imaging (MRI). We aimed to analyze the radiological features of patients with meningioma related to the simultaneous presence of bilateral macronodular adrenocortical disease (BMAD), with or without pathogenic variants of ARMC5.

METHODS

This study included 10 patients who were diagnosed with BMAD. All of them had a radiological diagnosis of expansive brain lesions suggestive of meningioma. All patients underwent brain MRI and a neuroradiolgist analyzed the following parameters: number, site and size of lesions; presence of calcification, edema and bone involvement.

RESULTS AND DISCUSSION

Eight patients presented with germline variants of ARMC5; the other 2, did not. The most significant result was the incidence of multiple meningiomas, which was 50% in BMAD patients, whereas the average incidence described thus far is lower than 10%. Considering location, the 22 tumors in the BMAD patients were 5 convexity tumors (22.7%), and 17 skull base tumors (77.2%), the opposite proportion of patients without BMAD. A total of 40.9% of the tumors had calcification, 9% had cerebral edema and 40.9% had bone invasion due to hyperostosis. The literature describes meningioma calcification in 25% of patients, bone invasion by tumor hyperostosis in 20%, and cerebral edema in approximately 60%.

CONCLUSION

Relevant results were found considering the rate of multiple meningiomas and tumor location. This finding reinforces the need for further research into the neurological effects caused by genetic variants of ARMC5 in patients with BMAD.

CBX7 reprograms metabolic flux to protect against meningioma progression by modulating the USP44/c-MYC/LDHA axis

Meningioma is one of the most common primary neoplasms in the central nervous system, but no specific molecularly targeted therapy has been approved for the clinical treatment of aggressive meningiomas. There is hence an urgent demand to decrypt the biological and molecular landscape of malignant meningioma. Here, through the in-silica prescreening and 10-year follow-up studies of 445 meningioma patients, we uncovered that CBX7 expression progressively decreases with malignancy grade and neoplasia stage in meningioma, and a high CBX7 expression level predicts a favorable prognosis in meningioma patients. CBX7 restoration significantly induces cell cycle arrest and inhibits meningioma cell proliferation. iTRAQ-based proteomics analysis indicated that CBX7 restoration triggers the metabolic shift from glycolysis to oxidative phosphorylation. The mechanistic study demonstrated that CBX7 promotes the proteasome-dependent degradation of c-MYC protein by transcriptionally inhibiting the expression of a c-MYC deubiquitinase, USP44, consequently attenuates c-MYC-mediated transactivation of LDHA transcripts, and further inhibits glycolysis and subsequent cell proliferation. More importantly, the functional role of CBX7 was further confirmed in subcutaneous and orthotopic meningioma xenograft mouse models and meningioma patients. Altogether, our results shed light on the critical role of CBX7 in meningioma malignancy progression and identify the CBX7/USP44/c-MYC/LDHA axis as a promising therapeutic target against meningioma progression.

NF2 mutation associated with accelerated time to recurrence for older patients with atypical meningiomas

PURPOSE

Meningiomas occur more frequently in older adults, with the incidence rates increasing from 5.8/100,000 for adults 35-44 years old to 55.2/100,000 for those 85+. Due to the increased risk of surgical management in older adults, there is a need to characterize the risk factors for aggressive disease course to inform management decisions in this population. We therefore sought to determine age-stratified relationships between tumour genomics and recurrence after resection of atypical meningiomas.

METHODS

We identified 137 primary and recurrent Grade 2 meningiomas from our existing meningioma genomic sequencing database. We examined the differential distribution of genomic alterations in those older than 65 compared to younger. We then performed an age stratified survival analysis to model recurrence for a mutation identified as differentially present.

RESULTS

In our cohort of 137 patients with grade 2 meningiomas, alterations in NF2 were present at a higher rate in older adults compared to younger (37.8% in < 65 vs. 55.3% in > 65; recurrence adjusted p-value =0.04). There was no association between the presence of NF2 and recurrence in the whole cohort. In the age-stratified model for those less than 65 years old, there was again no relationship. For patients in the older age stratum, there is a relationship between NF2 and worsened recurrence outcomes (HR = 3.64 (1.125 - 11.811); p = 0.031).

CONCLUSIONS

We found that mutations in NF2 were more common in older adults. Further, the presence of mutant NF2 was associated with an increased risk of recurrence in older adults.

ACSM3 suppresses proliferation and induces apoptosis and cell cycle arrest in acute myeloid leukemia cells via the regulation of IGF2BP2

Acyl-CoA medium-chain synthetase-3 (ACSM3) has been reported to be involved in the malignant progression of multiple types of human cancer. Nevertheless, the role of ACSM3 in acute myeloid leukemia (AML) and its exact mechanism of action are as yet undefined. In the present study, the expression levels of ACSM3 and IGF2 mRNA-binding protein 2 (IGF2BP2) were evaluated using the Gene Expression Profiling Interactive Analysis database and AML cells. The Cell Counting Kit-8 assay and 5-ethynyl-2'-deoxyuridine staining were employed for the estimation of the cell proliferative activity. Induction of apoptosis and the assessment of the cell cycle were measured using flow cytometry and western blotting, respectively. The interaction of ACSM3 with IGF2BP2 was confirmed using an RNA immunoprecipitation assay. mRNA stabilization of ACSM3 following actinomycin D treatment was evaluated using reverse transcription-quantitative PCR analysis. The data indicated that the expression levels of ACSM3 were significantly downregulated, whereas those of IGF2BP2 were upregulated in tissues and AML cells. Downregulation of ACSM3 expression was closely associated with poor overall survival of patients with AML. ACSM3 overexpression repressed cell proliferative activity and induced apoptosis and cell cycle arrest. IGF2BP2 downregulated ACSM3 expression by reducing the stability of ACSM3 mRNA. In addition, IGF2BP2 overexpression counteracted the effects of ACSM3 overexpression noted on proliferation, induction of apoptosis and cell cycle arrest of HL-60 cells. In conclusion, ACSM3 repressed the cell proliferative activity and facilitated induction of apoptosis and cell cycle arrest in AML cells by modulating the expression of IGF2BP2.

Evaluating risk of recurrence in patients with meningioma

OBJECTIVE

Meningioma prognostication and treatment continues to evolve with an increasing understanding of tumor biology. In this study, the authors aimed to test conventional predictors of meningioma recurrence, histopathology variables for which there exists some controversy (brain invasion), as well as a novel molecular-based location paradigm.

METHODS

This is a retrospective study of a consecutive series of patients with WHO grade I-III meningioma resected at The University of Texas Southwestern Medical Center between 1994 and 2015. Time to meningioma recurrence (i.e., recurrence-free survival [RFS]) was the primary endpoint measured. Kaplan-Meier curves were constructed and compared using log-rank tests. Cox univariate and multivariate analyses were performed to identify predictors of RFS.

RESULTS

A total of 703 consecutive patients with meningioma underwent resection at The University of Texas Southwestern Medical Center between the years 1994 and 2015. A total of 158 patients were excluded for insufficient follow-up (< 3 months). The median age of the cohort was 55 years (range 16-88 years) and 69.5% (n = 379) were female. The median follow-up was 48 months (range 3-289 months). There was not a significantly increased risk of recurrence in patients with evidence of brain invasion, in patients with otherwise WHO grade I meningioma (Cox univariate HR 0.92, 95% CI 0.44-1.91, p = 0.82, power 4.4%). Adjuvant radiosurgery to subtotally resected WHO grade I meningiomas did not prolong the time to recurrence (n = 52, Cox univariate HR 0.21, 95% CI 0.03-1.61, p = 0.13, power 71.6%). Location (midline skull base, lateral skull base, and paravenous) was significantly associated with RFS (p < 0.01, log-rank test). In patients with high-grade meningiomas (WHO grade II or III), location was predictive of RFS (p = 0.03, log-rank test), with paravenous meningiomas exhibiting the highest rates of recurrence. Location was not significant on multivariate analysis.

CONCLUSIONS

The data suggest that brain invasion does not increase the risk of recurrence in otherwise WHO grade I meningioma. Adjuvant radiosurgery to subtotally resected WHO grade I meningiomas did not prolong the time to recurrence. Location categorized by distinct molecular signatures did not predict RFS in a multivariate model. Larger studies are needed to confirm these findings.

Mutational signature of extracranial meningioma metastases and their respective primary tumors

Extracranial metastases of intracranial meningiomas are rare. Little is known about the mutational pattern of these tumors and their metastatic seeding. Here, we retrospectively explored the molecular alterations of these metastatic lesions and their respective intracranial tumor manifestations.Histology and genome sequencing were performed in intracranial meningiomas and their extracranial metastatic lesions operated upon between 2002 and 2021. Next-generation DNA/RNA sequencing (NGS) and methylome analysis were performed to determine molecular alterations.We analyzed the tumors of five patients with clinically suspected metastases of a meningioma using methylome analysis and next generation panel sequencing of the primary tumors as well as the metastatic lesions. Metastases were found in the spinal cord and one in the lung. In four of these patients, molecular analyses confirmed metastatic disease, while the fifth patient was found to harbor two molecularly distinct meningiomas. On pathological assessment, the primary lesions ranged from CNS WHO grades 1 to 3 (integrated molecular-morphologic meningioma classification scores 2 to 6). Of the four true metastatic cases, three out of the four metastasizing tumors harbored alterations in the BAP1 gene, comprising a stop-mutation combined with copy-number loss (WHO grade 1), copy number loss (WHO grade 3) and a frameshift mutation (WHO grade 2). Furthermore, the latter was confirmed to harbor a BAP1 tumor predisposition syndrome. The fourth metastasizing tumor had copy-number losses in NF2 and PTEN. Only one of four showed CDKN2A homozygous deletion; none showed TERT promotor mutation.Our results molecularly confirm true metastatic disease in four meningioma patients. BAP1 gene alterations were the most frequent. Larger cohorts, most likely from multicenter studies are necessary to evaluate the role of BAP-1 alterations to further understand the metastatic spread in meningiomas. for metastatic spread and might indicate patients at risk for metastatic spread. Further explorations within larger cohorts are necessary to validate these findings which might influence the clinical management in the future.

Recent advances in the molecular prognostication of meningiomas

Meningiomas are the most common primary intracranial neoplasm. While traditionally viewed as benign, meningiomas are associated with significant patient morbidity, and certain meningioma subgroups display more aggressive and malignant behavior with higher rates of recurrence. Historically, the risk stratification of meningioma recurrence has been primarily associated with the World Health Organization histopathological grade and surgical extent of resection. However, a growing body of literature has highlighted the value of utilizing molecular characteristics to assess meningioma aggressiveness and recurrence risk. In this review, we discuss preclinical and clinical evidence surrounding the use of molecular classification schemes for meningioma prognostication. We also highlight how molecular data may inform meningioma treatment strategies and future directions.

Paradigm Shift in the Treatment of Meningiomas

Meningiomas are the most common brain tumor in adults with rising incidence rates due to an aging population globally, increased availability of neuroimaging, and increased awareness of this condition by treating clinicians and primary care physicians. Surgical resection remains the mainstay of treatment, with adjuvant radiotherapy reserved for higher grade meningiomas or tumors that undergo incomplete resections. Whereas these tumors were classically defined by their histopathological features and subtypes, recent work has uncovered the molecular alterations that may lead to tumor development and have important prognostic implications. However, there remain important clinical questions regarding the management of meningiomas and current clinical guidelines continue to evolve as additional studies add onto the growing body of work that enables us to better understand these tumors.

Immunotherapy for Meningiomas

Systemic treatment approaches are urgently needed for a subset of meningioma patients who do not achieve local tumor control with surgery and radiotherapy. Classical chemotherapy or anti-angiogenic agents exert only very limited activity in these tumors. Long-term survival of patients with advanced metastatic cancer following treatment with immune checkpoint inhibitors, i.e., monoclonal antibodies designed to unleash suppressed anticancer immune responses, has fostered hopes for benefit from similar approaches in patients with meningiomas that recur after standard local therapy. Moreover, a plethora of immunotherapy approaches beyond these drugs have entered clinical development or clinical practice for other cancer entities, including (i) novel immune checkpoint inhibitors that may act independently of T cell activity, (ii) cancer peptide or dendritic cell vaccines to induce anticancer immunity utilizing cancer-associated antigens, (iii) cellular therapies utilizing genetically modified peripheral blood cells to directly target cancer cells, (iv) T cell engaging recombinant proteins that link tumor antigen-binding sites to effector cell activating or recognition domains, or to immunogenic cytokines, and (v) oncolytic virotherapy utilizing attenuated viral vectors designed to specifically infect cancer cells, seeking to elicit systemic anticancer immunity. This chapter provides an overview of the principles of immunotherapy, summarizes ongoing immunotherapy clinical trials in meningioma patients, and discusses the applicability of established and emerging immunotherapy concepts to meningioma patients.

Distinct clinical outcome of microcystic meningioma as a WHO grade 1 meningioma subtype

OBJECTIVE

To evaluate the clinicopathological characteristics, radiology, and long-term outcomes of microcystic meningiomas (MM) and compare it with other subtypes of meningiomas managed at a single neurosurgical center.

METHODS

A total of 87 consecutive patients who underwent surgical resection and were diagnosed as MM between 2005 and 2016 were enrolled for analysis. Clinicopathological, radiology, and prognostic information was collected and analyzed. Progression free survival (PFS) was compared with 659 patients with other subtypes of WHO grade 1 meningiomas and 167 patients with atypical meningiomas treated during the same period.

RESULTS

Fifty six females and 31 males with MM were analyzed. Peri-tumor brain edema was frequent on T2 WI (85%).12 patients (13.8%) experienced tumor progression during the mean follow-up of 101.66 ± 40.92 months. The median PFS was unavailable, and the 5, 10, and 15 year progression-free rates were 96.9%, 84.0%, and 73.9%, respectively. Univariate COX analysis demonstrated skull base location and higher Ki-67 index as significant negative prognostic factors for PFS (P < 0.05); multivariate analysis identified tumor location and Ki-67 index as independent factors (P < 0.01), as well. Of note, the PFS of MM was worse than other WHO grade 1 subtypes (P < 0.001), but better than atypical meningiomas (P < 0.001), and the PFS differences were retained even when the analysis was limited to the patients receiving GTR (P < 0.05).

CONCLUSION

The PFS of MM was worse than other WHO grade 1 subtypes and better than atypical meningiomas. Skull base location and higher Ki-67 index were independent negative prognostic factors in MM.

Radiation-Induced Meningiomas

While the majority of meningiomas encountered clinically are sporadic, there is a rare subset that arises due to early life or childhood irradiation. Sources of this radiation exposure may be due to treatment of other cancers such as acute childhood leukemia, other central nervous system tumors such as medulloblastoma, the treatment of tinea capitis (rarely and historically), or environmental exposures, as seen in some of the Hiroshima and Nagasaki atomic bomb survivors. Regardless of their etiology, however, radiation-induced meningiomas (RIMs) tend to be highly biologically aggressive irrespective of WHO grade and are usually refractory to the conventional treatment modalities of surgery and/or radiotherapy. In this chapter, we will discuss these RIMs in their historical context, their clinical presentation, their genomic features and ongoing efforts to better understand these tumors from a biological standpoint in order to develop better, more efficacious therapies for these patients.

The multiomic landscape of meningiomas: a review and update

PURPOSE

Meningiomas are the most common primary brain tumor in adults. Traditionally they have been understudied compared to other central nervous system (CNS) tumors. However over the last decade, there has been renewed interest in uncovering the molecular topography of these tumors, with landmark studies identifying key driver alterations contributing to meningioma development and progression. Recent work from several independent research groups have integrated different genomic and epigenomic platforms to develop a molecular-based classification scheme for meningiomas that could supersede histopathological grading in terms of diagnostic accuracy, biological relevance, and outcome prediction, keeping pace with contemporary grading schemes for other CNS tumors including gliomas and medulloblastomas.

METHODS

Here we summarize the studies that have uncovered key alterations in meningiomas which builds towards the discovery of consensus molecular groups in meningiomas by integrating these findings. These groups supersede WHO grade and other clinical factors in being able to accurately predict tumor biology and clinical outcomes following surgery.

RESULTS

Despite differences in the nomenclature of recently uncovered molecular groups across different studies, the biological similarities between these groups enables us to likely reconciliate these groups into four consensus molecular groups: two benign groups largely dichotomized by NF2-status, and two clinically aggressive groups defined by their hypermetabolic transcriptome, and by their preponderance of proliferative, cell-cycling pathways respectively.

CONCLUSION

Future work, including by our group and others are underway to validate these molecular groups and harmonize the nomenclature for routine clinical use.

Specific gene expression signatures of low grade meningiomas

Introduction

Meningiomas are the most common primary central nervous system (CNS) tumors in adults, representing approximately one-third of all primary adult CNS tumors. Although several recent publications have proposed alternative grading systems of meningiomas that incorporate genomic and/or epigenomic data to better predict meningioma recurrence and progression-free survival, our understanding of driving forces of meningioma development is still limited.

Objective

To define gene expression signatures of the most common subtypes of meningiomas to better understand cellular processes and signaling pathways specific for each tumor genotype.

Methods

We used RNA sequencing (RNA-seq) to determine whole transcriptome profiles of twenty meningiomas with genomic alterations including NF2 inactivation, loss of chr1p, and missense mutations in TRAF7, AKT1 and KLF4.

Results

The analysis revealed that meningiomas with NF2 gene inactivation expressed higher levels of BCL2 and GLI1 compared with tumors harboring TRAF7 missense mutations. Moreover, NF2 meningiomas were subdivided into two distinct groups based on additional loss of chr1p. NF2 tumors with intact chr1p were characterized by the high expression of tumor suppressor PTCH2 compared to NF2 tumors with chr1p loss. Taken together with the high expression of BCL2 and GLI1, these results suggest that activation of Sonic Hedgehog pathway may contribute to NF2 meningioma development. In contrast, NF2 tumors with chr1p loss expressed high levels of transcription factor FOXD3 and its antisense RNA FOXD3-AS1. Examination of TRAF7 tumors demonstrated that TRAF7 regulates a number of biomechanically responsive genes (KRT6a, KRT16, IL1RL1, and AQP3 among others). Interestingly, AKT1 and KLF4 meningiomas expressed genes specific for PI3K/AKT signaling pathway, suggesting overlapping gene signatures between the two subtypes. In addition, KLF4 meningiomas had high expression of carcinoembryonic antigen family members CEACAM6 and CEACAM5.

Conclusions

Each group of meningiomas displayed a unique gene expression signature suggesting signaling pathways potentially implicated in tumorigenesis. These findings will improve our understanding of meningioma tumorigenesis and prognosis.

Preclinical Models of Meningioma

The management of clinically aggressive meningiomas remains challenging due to limited treatment options aside from surgical removal and radiotherapy. High recurrence rates and lack of effective systemic therapies contribute to the unfavorable prognosis of these patients. Accurate in vitro and in vivo models are critical for understanding meningioma pathogenesis and to identify and test novel therapeutics. In this chapter, we review cell models, genetically engineered mouse models, and xenograft mouse models, with special emphasis on the field of application. Finally, promising preclinical 3D models such as organotypic tumor slices and patient-derived tumor organoids are discussed.

Brain Invasion and Trends in Molecular Research on Meningioma

Meningiomas are the most common primary brain tumors in adults. The treatment of non-benign meningiomas remains a challenging task, and after the publication of the 2021 World Health Organization classification, the importance of molecular biological classification is emerging. In this article, we introduce the mechanisms of brain invasion in atypical meningioma and review the genetic factors involved along with epigenetic regulation. First, it is important to understand the three major steps for brain invasion of meningeal cells: 1) degradation of extracellular matrix by proteases, 2) promotion of tumor cell migration to resident cells by adhesion molecules, and 3) neovascularization and supporting cells by growth factors. Second, the genomic landscape of meningiomas should be analyzed by major categories, such as germline mutations in NF2 and somatic mutations in non-NF2 genes (TRAF7, KLF4, AKT1, SMO, and POLR2A). Finally, epigenetic alterations in meningiomas are being studied, with a focus on DNA methylation, histone modification, and RNA interference. Increasing knowledge of the molecular landscape of meningiomas has allowed the identification of prognostic and predictive markers that can guide therapeutic decision-making processes and the timing of follow-up.

Loss of H3K27me3 expression enriches in recurrent grade 1&2 meningiomas and maintains as a biomarker stratifying progression risk

PURPOSE

To determine if loss of H3K27me3 could predict higher risk of re-recurrence in recurrent meningiomas.

METHODS

A retrospective, single-center cohort study was performed for patients who underwent resection of recurrent grade 1 (N = 132) &2 (N = 32) meningiomas from 2009 to 2013. Association of H3K27me3 staining and clinical parameters was analyzed. Additionally, H3K27me3 staining was performed from 45 patients whose tumors recurred and were resected during the follow-up, to evaluate H3K27me3 change during tumor progression. Survival analysis was performed as well.

RESULTS

Loss of H3K27me3 expression was observed in 83 patients, comprising 63 grade 1 (47.7%) and 20 grade 2 patients (62.5%). Both grade 1 (p < 0.001) and grade 2 recurrent meningiomas (p < 0.001) had a higher frequency of H3K27me3 loss, compared to de novo meningiomas. 8 of 27 tumors with retained H3K27me3 lost H3K27me3 during re-recurrence (29.6%), while no gain of H3K27me3 was observed in progressive disease from 18 tumors with H3K27me3 loss. Loss of H3K27me3 expression was associated with an earlier re-recurrence in recurrent meningiomas grade 1 and 2 (p < 0.001), and was an independent prognostic factor for PFS in recurrent grade 1 meningiomas (p = 0.005).

CONCLUSION

Compared to primary meningiomas, recurrent meningiomas more predominantly had loss of H3K27me3 expression, and further loss can occur during the progression of recurrent tumors. Our results further demonstrated that loss of H3K27me3 predicted shorter PFS in recurrent grade 1 and grade 2 meningiomas. Our work thus supports clinical testing of H3K27me3 in recurrent meningiomas WHO grade 1 and 2.

Prognostic significance of telomerase reverse transcriptase promoter gen mutations in high grade meningiomas

Introduction: Mutations in the promoter region of telomerase reverse transcriptase occur frequently in meningiomas. Objective: To estimate the prognostic importance of telomerase reverse transcriptase mutations in Colombian patients with grades II and III meningioma. Materials and methods: This was a multicenter retrospective cohort study of patients diagnosed with refractory or recurrent WHO grades II and III meningiomas, recruited between 2011 and 2018, and treated with systemic therapy (sunitinib, everolimus ± octreotide, and bevacizumab). Mutation status of the telomerase reverse transcriptase promoter was established by PCR. Results: Forty patients were included, of which telomerase reverse transcriptase mutations were found in 21 (52.5%), being C228T and C250T the most frequent variants with 87.5 % and 14.3 %, respectively. These were more frequent among patients with anaplastic meningiomas (p=0.18), with more than 2 recurrences (p=0.04); and in patients with parasagittal region and anterior fossa lesions (p=0.05). Subjects characterized as having punctual mutations were more frequently administered with everolimus, sunitinib and bevacizumab drug series (p=0.06). Overall survival was 23.7 months (CI95% 13.1-34.2) and 43.4 months (CI95% 37.5-49.3; p=0.0001) between subjects with and without mutations, respectively. Multivariate analysis showed that the number of recurrences and the presence of telomerase reverse transcriptase mutations were tthe only variables that negatively affected overall survival. Conclusions: Mutations in telomerase reverse transcriptase allows the identification of high-risk patients and could be useful in the selection of the best medical treatment.

Clinical Management of Supratentorial Non-Skull Base Meningiomas

Supratentorial non-skull base meningiomas are the most common primary central nervous system tumor subtype. An understanding of their pathophysiology, imaging characteristics, and clinical management options will prove of substantial value to the multi-disciplinary team which may be involved in their care. Extensive review of the broad literature on the topic is conducted. Narrowing the scope to meningiomas located in the supratentorial non-skull base anatomic location highlights nuances specific to this tumor subtype. Advances in our understanding of the natural history of the disease and how findings from both molecular pathology and neuroimaging have impacted our understanding are discussed. Clinical management and the rationale underlying specific approaches including observation, surgery, radiation, and investigational systemic therapies is covered in detail. Future directions for probable advances in the near and intermediate term are reviewed.

Radiotherapy for meningiomas

Meningiomas are the most common primary central nervous system neoplasm. Despite promising recent progress in elucidating the genomic landscape and underlying biology of these histologically, molecularly, and clinically diverse tumors, the mainstays of meningioma treatment remain maximal safe resection and radiation therapy. The aim of this review of meningioma radiotherapy is to provide a concise summary of the history, current evidence, and future for application of radiotherapy in meningioma treatment.

Mutated KLF4(K409Q) in meningioma binds STRs and activates FGF3 gene expression

Krüppel-like factor 4 (KLF4) is a transcription factor that has been proven necessary for both induction and maintenance of pluripotency and self-renewal. Whole-genome sequencing defined a unique mutation in KLF4 (KLF4K409Q) in human meningiomas. However, the molecular mechanism of this tumor-specific KLF4 mutation is unknown. Using genome-wide high-throughput and focused quantitative transcriptional approaches in human cell lines, primary meningeal cells, and meningioma tumor tissue, we found that a change in the evolutionarily conserved DNA-binding domain of KLF4 alters its DNA recognition preference, resulting in a shift in downstream transcriptional activity. In the KLF4K409Q-specific targets, the normally silent fibroblast growth factor 3 (FGF3) is activated. We demonstrated a neomorphic function of KLF4K409Q in stimulating FGF3 transcription through binding to its promoter and in using short tandem repeats (STRs) located within the locus as enhancers.

Skull Base Meningiomas in Patients with Neurofibromatosis Type 2: An International Multicenter Study Evaluating Stereotactic Radiosurgery

Objective  Meningiomas are the second most common tumors in neurofibromatosis type 2 (NF-2). Microsurgery is challenging in NF-2 patients presenting with skull base meningiomas due to the intrinsic risks and need for multiple interventions over time. We analyzed treatment outcomes and complications after primary Gamma Knife radiosurgery (GKRS) to delineate its role in the management of these tumors. Methods  An international multicenter retrospective study approved by the International Radiosurgery Research Foundation was performed. NF-2 patients with at least one growing and/or symptomatic skull base meningioma and 6-month follow-up after primary GKRS were included. Clinical and radiosurgical parameters were recorded for analysis. Results  In total, 22 NF-2 patients with 54 skull base meningiomas receiving GKRS as primary treatment met inclusion criteria. Median age at GKRS was 38 years (10-79 years). Most lesions were located in the posterior fossa (55.6%). Actuarial progression free survival (PFS) rates were 98.1% at 2 years and 90.0% at 5 and 10 years. The median follow-up time after initial GKRS was 5.0 years (0.6-25.5 years). Tumor volume at GKRS was a predictor of tumor control. Lesions >5.5 cc presented higher chances to progress after radiosurgery ( p  = 0.043). Three patients (13.64%) developed adverse radiation effects. No malignant transformation or death due to meningioma or radiosurgery was reported. Conclusions  GKRS is effective and safe in the management of skull base meningiomas in NF-2 patients. Tumor volume deserve greater relevance during clinical decision-making regarding the most appropriate time to treat. GKRS offers a minimally invasive approach of particular interest in this specific group of patients.

Meningioma DNA methylation groups identify biological drivers and therapeutic vulnerabilities

Meningiomas are the most common primary intracranial tumors. There are no effective medical therapies for meningioma patients, and new treatments have been encumbered by limited understanding of meningioma biology. Here, we use DNA methylation profiling on 565 meningiomas integrated with genetic, transcriptomic, biochemical, proteomic and single-cell approaches to show meningiomas are composed of three DNA methylation groups with distinct clinical outcomes, biological drivers and therapeutic vulnerabilities. Merlin-intact meningiomas (34%) have the best outcomes and are distinguished by NF2/Merlin regulation of susceptibility to cytotoxic therapy. Immune-enriched meningiomas (38%) have intermediate outcomes and are distinguished by immune infiltration, HLA expression and lymphatic vessels. Hypermitotic meningiomas (28%) have the worst outcomes and are distinguished by convergent genetic and epigenetic mechanisms driving the cell cycle and resistance to cytotoxic therapy. To translate these findings into clinical practice, we show cytostatic cell cycle inhibitors attenuate meningioma growth in cell culture, organoids, xenografts and patients.

The Discrepancy Between Standard Histologic WHO Grading of Meningioma and Molecular Profile: A Single Institution Series

Introduction

Meningiomas are the most common primary central nervous system (CNS) tumor. They are most often benign, but a subset of these can behave aggressively. Current World Health Organization (WHO) guidelines classify meningiomas into three grades based on the histologic findings and presence or absence of brain invasion. These grades are intended to guide treatment, but meningiomas can behave inconsistently with regard to their assigned histopathological grade, influencing patient expectations and management. Advanced molecular profiling of meningiomas has led to the proposal of alternative molecular grading schemes that have shown superior predictive power. These include methylation patterns, copy number alterations, and mutually exclusive driver mutations affecting oncogenes, including BAP1, CDKN2A/B, and the TERT promoter, which are associated with particularly aggressive tumor biology. Despite the evident clinical value, advanced molecular profiling methods are not widely incorporated in routine clinical practice for meningiomas.

Objective

To assess the degree of concordance between the molecular profile of meningiomas and the histopathologic WHO classification, the current method of predicting meningioma behavior.

Methods

In a two-year single-institution experience, we used commercially available resources to determine molecular profiles of all resected meningiomas. Copy number aberrations and oncogenic driver mutations were identified and compared with the histopathologic grade.

Results

One hundred fifty-one total meningioma cases were included for analysis (85.4% WHO grade 1, 13.3% WHO grade 2, and 1.3% grade 3). Chromosomal analysis of 124 of these samples showed that 29% of WHO grade 1 tumor featured copy number profiles consistent with higher grade meningioma, and 25% of WHO grade 2 meningiomas had copy number profiles consistent with less aggressive tumors. Furthermore, 8% harbored mutations in TERT, CDKN2A/B, or BAP1 of which 6% occurred in grade 1 meningiomas.

Conclusions

Routine advanced molecular profiling of all resected meningiomas using commercially available resources allowed for identification of a significant number of meningiomas whose molecular profiles were inconsistent with WHO grade. Our work shows the clinical value of integrating routine molecular profiling with histopathologic grading to guide clinical decision making.

Skull Base Tumors: Neuropathology and Clinical Implications

Tumors that arise in and around the skull base comprise a wide range of common and rare entities. Recent studies have advanced our understanding of their pathogenesis, which in some cases, have significantly influenced clinical practice. The genotype of meningiomas is strongly associated with their phenotype, including histologic subtype and tumor location, and clinical outcome. A single molecular alteration, NAB2-STAT6 fusion, has redefined the category of solitary fibrous tumors to include the previous entity hemangiopericytomas. Schwannomas, both sporadic and familial, are characterized by near ubiquitous alterations in NF2 , with additional mutations in SMARCB1 or LZTR1 in schwannomatosis. In pituitary adenohypophyseal tumors, cell lineage transcription factors such as SF-1, T-PIT, and PIT-1 are now essential for classification, providing a more rigorous taxonomy for tumors that were previously considered null cell adenomas. The pituicyte lineage transcription factor TTF-1 defines neurohypophyseal tumors, which may represent a single nosological entity with a spectrum of morphologic manifestations (ie, granular cell tumor, pituicytoma, and spindle cell oncocytoma). Likewise, the notochord cell lineage transcription factor brachyury defines chordoma, discriminating them from chondrosarcomas. The identification of nonoverlapping genetic drivers of adamantinomatous craniopharyngiomas and papillary craniopharyngiomas indicates that these are distinct tumor entities and has led to successful targeted treatment of papillary craniopharyngiomas using BRAF and/or mitogen-activated protein kinase inhibitors. Similarly, dramatic therapeutic responses have been achieved in patients with Langerhans cell histiocytosis, both with BRAF -mutant and BRAF -wildtype tumors. Familiarity with the pathology of skull base tumors, their natural history, and molecular features is essential for optimizing patient care.

Whole-Exome Sequencing Reveals Recurrent but Heterogeneous Mutational Profiles in Sporadic WHO Grade 1 Meningiomas

Human WHO grade 1 meningiomas are generally considered benign tumors; despite this, they account for ≈50% of all recurrent meningiomas. Currently, limited data exist about the mutational profiles of grade 1 meningiomas and patient outcome. We investigated the genetic variants present in 32 WHO grade 1 meningiomas using whole exome sequencing, and correlated gene mutational profiles with tumor cytogenetics and patient outcome. Overall, WHO grade 1 meningiomas harbored numerous and heterogeneous genetic variants, which most frequently affected the NF2 (47%) gene and to a less extent the PNMA6A (22%), TIGD1 (16%), SMO (13%), PTEN (13%), CREG2 (9%), EEF1A1 (6%), POLR2A (6%), ARID1B (3%), and FAIM3 (3%) genes. Notably, non-synonymous genetic variants of SMO and POLR2A were restricted to diploid meningiomas, whereas NF2 mutations were only found among tumors that showed -22/22q^─ (with or without a complex karyotype). Based on NF2 mutations and tumor cytogenetics, four genetic profiles were defined with an impact on patient recurrence-free survival (RFS). These included (1) two good-prognosis tumor subgroups-diploid meningiomas (n=9) and isolated -22/22q^─ associated with NF2 mutation (n=7)-with RFS rates at 10 y of 100%; and (2) two subgroups of poor-prognosis meningiomas-isolated -22/22q^─ without NF2 mutation (n=3) and tumors with complex karyotypes (n=11)-with a RFS rate at 10 y of 48% (p=0.003). Our results point out the existence of recurrent but heterogeneous mutational profiles in WHO grade 1 meningiomas which have an impact on patient outcome.

Receptor Tyrosine Kinases as Candidate Prognostic Biomarkers and Therapeutic Targets in Meningioma

Meningioma (MGM) is the most common type of intracranial tumor in adults. The validation of novel prognostic biomarkers to better inform tumor stratification and clinical prognosis is urgently needed. Many molecular and cellular alterations have been described in MGM tumors over the past few years, providing a rational basis for the identification of biomarkers and therapeutic targets. The role of receptor tyrosine kinases (RTKs) as oncogenes, including those of the ErbB family of receptors, has been well established in several cancer types. Here, we review histological, molecular, and clinical evidence suggesting that RTKs, including the epidermal growth factor receptor (EGFR, ErbB1), as well as other members of the ErbB family, may be useful as biomarkers and therapeutic targets in MGM.

The Role of 3D Tractography in Skull Base Surgery: Technological Advances, Feasibility, and Early Clinical Assessment with Anterior Skull Base Meningiomas

Objective  The aim of this study is to determine feasibility of incorporating three-dimensional (3D) tractography into routine skull base surgery planning and analyze our early clinical experience in a subset of anterior cranial base meningiomas (ACM). Methods  Ninety-nine skull base endonasal and transcranial procedures were planned in 94 patients and retrospectively reviewed with a further analysis of the ACM subset. Main Outcome Measures  (1) Automated generation of 3D tractography; (2) co-registration 3D tractography with computed tomography (CT), CT angiography (CTA), and magnetic resonance imaging (MRI); and (3) demonstration of real-time manipulation of 3D tractography intraoperatively. ACM subset: (1) pre- and postoperative cranial nerve function, (2) qualitative assessment of white matter tract preservation, and (3) frontal lobe fluid-attenuated inversion recovery (FLAIR) signal abnormality. Results  Automated 3D tractography, with MRI, CT, and CTA overlay, was produced in all cases and was available intraoperatively. ACM subset : 8 (44%) procedures were performed via a ventral endoscopic endonasal approach (EEA) corridor and 12 (56%) via a dorsal anteromedial (DAM) transcranial corridor. Four cases (olfactory groove meningiomas) were managed with a combined, staged approach using ventral EEA and dorsal transcranial corridors. Average tumor volume reduction was 90.3 ± 15.0. Average FLAIR signal change was -30.9% ± 58.6. 11/12 (92%) patients (DAM subgroup) demonstrated preservation of, or improvement in, inferior fronto-occipital fasciculus volume. Functional cranial nerve recovery was 89% (all cases). Conclusion  It is feasible to incorporate 3D tractography into the skull base surgical armamentarium. The utility of this tool in improving outcomes will require further study.

Innumerable Meningiomas Arising in a Patient With Tuberous Sclerosis Complex Decades After Radiation Therapy

Meningioma is the most common radiation-induced brain neoplasm, usually occurring after a latency of 20 - 35 years, with multiplicity in 10% of cases. Radiation-induced meningiomas (RIMs) have not previously been reported in patients with tuberous sclerosis complex (TSC), unlike their well-known occurrence in other familial tumor predisposition syndrome patients. We report a TSC patient who developed numerous intracranial meningiomas twenty five year after radiation therapy for subependymal giant cell astrocytoma (SEGA). Autopsy examination showed innumerable, coalescent, benign, meningothelial meningiomas, WHO grade 1, ranging in size from 0.2 cm to 3.3 cm. Autopsy also showed small residual SEGA, radiation-induced cerebral vasculopathy, and classic TSC features including several small subependymal nodules ("candle gutterings"), white matter radial heterotopia, facial angiofibromas, dental enamel pitting, one ash leaf spot, and multiple hepatic and renal angiomyolipomas. Next-generation sequencing analysis utilizing a 500+ gene cancer panel demonstrated chromosomal loss involving the majority of chromosome 22, including the NF2 gene locus, as well as a truncating nonsense mutation in TSC1 p. R509*. While TSC patients rarely require radiation therapy, this striking case suggests that patients with TSC should be monitored closely if cranial therapeutic radiation is administered.

Comprehensive proteomic analysis reveals distinct functional modules associated with skull base and supratentorial meningiomas and perturbations in collagen pathway components

Meningiomas are brain tumors that originate from the meninges and has been primarily classified into three grades by the current WHO guidelines. Although widely prevalent and can be managed by surgery there are instances when the tumors are located in difficult regions. This results in considerable challenges for complete surgical resection and further clinical management. While the genetic signature of the skull base tumors is now known to be different from the non-skull base tumors, there is a lack of information at the functional aspects of these tumors at the proteomic level. Thus, the current study thereby aims to obtain mechanistic insights between the two radiologically distinct groups of meningiomas, namely the skull base & supratentorial (non-skull base-NSB) regions. We have employed a comprehensive mass spectrometry-based label-free quantitative proteomic analysis in Skull base and supratentorial meningiomas. Further, we have used an Artificial Neural Networking employing a sparse Multilayer perceptron (MLP) architecture to predict protein concordance. A patient-derived spectral library has been employed for a novel peptide-level validation of proteins that are specific to the radiological regions using the SRM assay based targeted proteomics approach. The comprehensive proteomics enabled the identification of nearly 4000 proteins with high confidence (1%FDR ≥ 2 unique peptides) among which 170 proteins were differentially abundant in Skull base vs Supratentorial tumors (p-value ≤0.05). In silico analysis enabled mapping of the major alterations and hinted towards an overall perturbation of extracellular matrix and collagen biosynthesis components in the non-skull base meningiomas and a prominent perturbation of molecular trafficking in the skull base meningiomas. Therefore, this study has yielded novel insights into the functional association of the proteins that are differentially abundant in the two radiological subgroups. SIGNIFICANCE: In the current study, we have performed label-free proteomic analysis on fresh frozen tissue of 14 Supratentorial (NSB) and 7 Skull base meningiomas to assess perturbations in the global proteome, we have further employed an in-depth in silico analysis to map the pathways that have enabled functional mapping of the differentially abundant proteins in the Skull base and Supratentorial tumors. The findings from the above were also subjected to a machine learning-based neural networking to find out the proteins that have the most concordance of occurrence to determine the most influential proteins of the network. We further validated the differential abundance of identified protein markers in a larger patient cohort of Skull base and Supratentorial employing targeted proteomics approach to validate key protein candidates emerging from ours and other recent studies. The previous studies that have explored the skull base and convexity meningiomas have been able to reveal alterations in the genetic mutations in these tumor types. However, there are not many studies that have explored the functional aspects of these tumors, especially at the proteome level. We have attempted for the first time to map the functional modules associated with altered proteins in these tumors and have been able to identify that there is a possibility that the Skull base meningiomas to be considerably different from the Non-skull base (NSB) tumors in terms of the perturbed pathways. Our study employed global as well as targeted proteomics to examine the proteomic alterations in these two tumor groups. The study indicates that proteins that were more abundant in Skull base tumors were part of molecular transport components, non-skull base proteins majorly mapped to the components of extracellular matrix remodeling pathways. In conclusion, this study substantiates the distinction in the proteomic signatures in the skull base and supratentorial meningiomas paving way for further investigation of the identified markers for determining if some of these proteins can be used for therapeutic interventions for cases that pose considerable challenges for complete resection.

Aggressive Radiation-Induced Cavernous Sinus Meningioma: 2-Dimensional Operative Video

Radiation-induced meningiomas are the most common radiation-induced neoplasms. They exhibit a distinct aggressive clinical behavior as rapid growth, recurrences, multiplicity, and malignant progression are common features.1-4 Atypical histological findings and aberrant cytogenetics are increasingly identified.5-7 Radical resection of aggressive radiation-induced meningiomas is the best treatment option and would offer the best chance for control of the disease. Wide bone and dural margins should be pursued in the resection. Parasellar extension creates significant surgical challenges. Cavernous sinus exploration through the multidirectional axis provided by the cranioorbital zygomatic approach allows radical resection of the tumor, cranial nerve decompression, and carotid artery preservation and control.8-11 This article describes a cavernous sinus radiation-induced meningioma after radiation for Cushing disease. It demonstrates the details of the extra- and intradural exploration and dissection of the neurovascular structures in the cavernous sinus, with proximal and distal control of the carotid artery. However, even after radical resection, recurrence is a common finding in this malignant behavioral radiation-induced tumor. Patient consented for surgery. Image at 9:41 comes from the Science Museum Group, United Kingdom. Refer to the Wellcome blog post (archive). This image is licensed under the CC-BY 4.0 International license.

Sarcomatous Meningioma: Diagnostic Pitfalls and the Utility of Molecular Testing

Anaplastic meningiomas can have a sarcomatous appearance on histology but true sarcomatous (metaplastic) differentiation is rare. These tumors follow an aggressive clinical course with recurrence and poor clinical outcomes. Due to significant overlap in morphology and immunohistochemical profiles, distinguishing between sarcomatous transformation of a meningioma and a true sarcoma can be challenging. Here, we outline potential diagnostic pitfalls and the utility of ancillary molecular testing in 3 patients diagnosed with sarcomatous meningiomas. We report loss of typical meningothelial markers in sarcomatous meningiomas. Ancillary molecular testing can support the diagnosis of sarcomatous meningioma when a molecular signature consistent with meningioma is seen, such as inactivation of the NF2 gene. Recognition of this rare transformation in meningioma can prevent a misdiagnosis of a primary sarcoma, whether sporadic or radiation-induced from prior treatment of a more classic meningioma.

GAB1 overexpression identifies hedgehog-activated anterior skull base meningiomas

AIMS

Mutations activating the hedgehog (Hh) signalling pathway have been described in anterior skull base meningiomas, raising hope for the use of targeted therapies. However, identification of Hh-activated tumours is hampered by the lack of a reliable immunohistochemical marker. We report the evaluation of GAB1, an immunohistochemical marker used to detect Hh pathway activation in medulloblastoma, as a potential marker of Hh-activated meningiomas.

METHODS

GAB1 staining was compared to SMO mutation detection with Sanger and NGS techniques as well as Hh pathway activation study through mRNA expression level analyses in a discovery set of 110 anterior skull base meningiomas and in a prospective validation set of 21 meningiomas.

RESULTS

Using an expression score ranging from 0 to 400, we show that a cut-off score of 250 lead to excellent detection of Hh pathway mutations (sensitivity 100%, specificity 86%). The prospective validation set confirmed the excellent negative predictive value of GAB1 to exclude Hh-independent meningiomas. We describe a large series of 32 SMO-mutant meningiomas and define multiple ways of Hh activation, either through somatic mutations or associated with mutually co-exclusive sonic hedgehog (SHH) or Indian hedgehog (IHH) overexpression independent of the mutations.

CONCLUSION

The assessment of GAB1 expression by an immunohistochemical score is a fast and cost-efficient tool to screen anterior skull base meningiomas for activation of the Hh pathway. It could facilitate the identification of selected cases amenable to sequencing for Hh pathway genes as predictive markers for targeted therapy.

Associations of pathological diagnosis and genetic abnormalities in meningiomas with the embryological origins of the meninges

Certain driver mutations and pathological diagnoses are associated with the anatomical site of meningioma, based on which the meninges have different embryological origins. We hypothesized that mutations and pathological diagnoses of meningiomas are associated with different embryological origins. We comprehensively evaluated associations among tumor location, pathological diagnosis (histological type), and genetic alterations including AKT1, KLF4, SMO, POLR2A, and NF2 mutations and 22q deletion in 269 meningioma cases. Based on the embryological origin of meninges, the tumor locations were as follows: neural crest, paraxial mesodermal, and dorsal mesodermal origins. Tumors originating from the dura of certain embryologic origin displayed a significantly different pathological diagnoses and genetic abnormality ratio. For instance, driver genetic mutations with AKT1, KLF4, SMO, and POLR2A, were significantly associated with the paraxial mesodermal origin (p = 1.7 × 10⁻¹⁰). However, meningiomas with NF2-associated mutations were significantly associated with neural crest origin (p = 3.9 × 10^–12). On analysis of recurrence, no difference was observed in embryological origin. However, POLR2A mutation was a risk factor for the tumor recurrence (p = 1.7 × 10⁻², Hazard Ratio 4.08, 95% Confidence Interval 1.28–13.0). Assessment of the embryological origin of the meninges may provide novel insights into the pathomechanism of meningiomas.

Convexity Meningiomas in Patients with Neurofibromatosis Type 2: Long-Term Outcomes After Gamma Knife Radiosurgery

BACKGROUND

Convexity meningiomas are common tumors requiring treatment in patients with neurofibromatosis type 2 (NF2). Although different therapeutic options are described for sporadic convexity meningioma, much less is known about these lesions in patients with NF2 despite their distinct biology and need for multiple treatments. We analyzed the value of Gamma Knife radiosurgery (GKRS) as definitive treatment for convexity meningiomas in patients with NF2.

METHODS

This international multicenter retrospective study was approved by the International Radiosurgery Research Foundation. Patients with NF2 with at least 1 convexity meningioma and 6-month follow-up after primary GKRS were included.

RESULTS

Inclusion criteria were met by 18 patients with NF2. A total of 120 convexity meningiomas (median treatment volume, 0.66 cm3 [range, 0.10-21.20 cm3]) were analyzed. Median follow-up after initial GKRS was 15.6 years (range, 0.6-25.5 years). Median age at GKRS was 32.5 years (range, 16-53 years). Median number of meningiomas per patient was 13 (range, 1-27), and median number of convexity lesions receiving GKRS per patient was 3.5 (range, 1-27). One case of tumor progression was reported 24 years after GKRS, leading to actuarial progression-free survival rates of 100% at 2, 5, and 10 years. No malignant transformation or death due to meningioma or radiosurgery was recorded.

CONCLUSIONS

GKRS is safe and effective as definitive treatment of small to medium-sized convexity meningiomas in patients with NF2. Despite concerns about the particular mutational burden of these tumors, no malignant transformation manifested after treatment. GKRS represents a minimally invasive option that offers long-term tumor control to this specific group of patients.

Neurofibromatosis Type 2 (NF2) and the Implications for Vestibular Schwannoma and Meningioma Pathogenesis

Patients diagnosed with neurofibromatosis type 2 (NF2) are extremely likely to develop meningiomas, in addition to vestibular schwannomas. Meningiomas are a common primary brain tumor; many NF2 patients suffer from multiple meningiomas. In NF2, patients have mutations in the NF2 gene, specifically with loss of function in a tumor-suppressor protein that has a number of synonymous names, including: Merlin, Neurofibromin 2, and schwannomin. Merlin is a 70 kDa protein that has 10 different isoforms. The Hippo Tumor Suppressor pathway is regulated upstream by Merlin. This pathway is critical in regulating cell proliferation and apoptosis, characteristics that are important for tumor progression. Mutations of the NF2 gene are strongly associated with NF2 diagnosis, leading to benign proliferative conditions such as vestibular schwannomas and meningiomas. Unfortunately, even though these tumors are benign, they are associated with significant morbidity and the potential for early mortality. In this review, we aim to encompass meningiomas and vestibular schwannomas as they pertain to NF2 by assessing molecular genetics, common tumor types, and tumor pathogenesis.

Alteration of FOXM1 expression and macrophage polarization in refractory meningiomas during long-term follow-up

Malignant progression of grade I meningioma with a long latency period is rare. We experienced grade II/III meningiomas with refractoriness and recurrence from grade I meningiomas through multiple surgeries. Three patients with atypical/anaplastic meningioma experienced long-latent recurrence after initial surgery for grade I (meningothelial) meningioma without following adjuvant radiotherapy were included in the present study. Histological findings of the initial tumors in all cases (case 1, 2, and 3) revealed meningothelial meningioma with 1%, 5%, and 0.1% MIB-1 positive cells, respectively. Surprisingly, magnetic resonance imaging (MRI) detected a recurrent tumor 2, 12, and 12 years after the initial operation, respectively. Case 1 was atypical meningioma after third recurrence, and case 2 and 3 were anaplastic meningioma after second and third recurrence, respectively. The patient in case 2 received adjuvant radiotherapy. In case 2, the tumor recurred intracranial and distant metastasis to the lung with huge substantial pleural effusion was detected. To investigate the pathogenesis of malignant progression from benign to malignant meningioma, CD163/CD68 expression by immunohistochemically and FOXM1 mRNA expression by RT-PCR were compared using surgical specimens from initial and recurrent tumors in all three patients. The ratio of CD163/CD68 positivity and FOXM1 mRNA expression were increased in recurrent tumors compared with matched initial tumors. CD163 and FOXM1 expression levels were induced even in recurrent grade I meningioma, suggesting that macrophage polarization and pro-mitotic transcriptional factor might be associated with clinical behavior of meningioma and be useful as a prediction marker for malignant progression. Careful long-term follow-up is important for early diagnosis of malignant progression in meningiomas, even if grade I meningioma is completely resected. Development of a multidisciplinary approach including radiation and novel molecular targeted therapy is expected for recurrent and malignant meningiomas.

A Prognostic Gene-Expression Signature and Risk Score for Meningioma Recurrence After Resection

BACKGROUND

Prognostic markers for meningioma are needed to risk-stratify patients and guide postoperative surveillance and adjuvant therapy.

OBJECTIVE

To identify a prognostic gene signature for meningioma recurrence and mortality after resection using targeted gene-expression analysis.

METHODS

Targeted gene-expression analysis was used to interrogate a discovery cohort of 96 meningiomas and an independent validation cohort of 56 meningiomas with comprehensive clinical follow-up data from separate institutions. Bioinformatic analysis was used to identify prognostic genes and generate a gene-signature risk score between 0 and 1 for local recurrence.

RESULTS

We identified a 36-gene signature of meningioma recurrence after resection that achieved an area under the curve of 0.86 in identifying tumors at risk for adverse clinical outcomes. The gene-signature risk score compared favorably to World Health Organization (WHO) grade in stratifying cases by local freedom from recurrence (LFFR, P < .001 vs .09, log-rank test), shorter time to failure (TTF, F-test, P < .0001), and overall survival (OS, P < .0001 vs .07) and was independently associated with worse LFFR (relative risk [RR] 1.56, 95% CI 1.30-1.90) and OS (RR 1.32, 95% CI 1.07-1.64), after adjusting for clinical covariates. When tested on an independent validation cohort, the gene-signature risk score remained associated with shorter TTF (F-test, P = .002), compared favorably to WHO grade in stratifying cases by OS (P = .003 vs P = .10), and was significantly associated with worse OS (RR 1.86, 95% CI 1.19-2.88) on multivariate analysis.

CONCLUSION

The prognostic meningioma gene-expression signature and risk score presented may be useful for identifying patients at risk for recurrence.

Multiplatform genomic profiling and magnetic resonance imaging identify mechanisms underlying intratumor heterogeneity in meningioma

Meningiomas are the most common primary intracranial tumors, but the molecular drivers of meningioma tumorigenesis are poorly understood. We hypothesized that investigating intratumor heterogeneity in meningiomas would elucidate biologic drivers and reveal new targets for molecular therapy. To test this hypothesis, here we perform multiplatform molecular profiling of 86 spatially-distinct samples from 13 human meningiomas. Our data reveal that regional alterations in chromosome structure underlie clonal transcriptomic, epigenomic, and histopathologic signatures in meningioma. Stereotactic co-registration of sample coordinates to preoperative magnetic resonance images further suggest that high apparent diffusion coefficient (ADC) distinguishes meningioma regions with proliferating cells enriched for developmental gene expression programs. To understand the function of these genes in meningioma, we develop a human cerebral organoid model of meningioma and validate the high ADC marker genes CDH2 and PTPRZ1 as potential targets for meningioma therapy using live imaging, single cell RNA sequencing, CRISPR interference, and pharmacology.

Comprehending Meningioma Signaling Cascades Using Multipronged Proteomics Approaches & Targeted Validation of Potential Markers

Meningiomas are one of the most prevalent primary brain tumors. Our study aims to obtain mechanistic insights of meningioma pathobiology using mass spectrometry-based label-free quantitative proteome analysis to identifying druggable targets and perturbed pathways for therapeutic intervention. Label-free based proteomics study was done from peptide samples of 21 patients and 8 non-tumor controls which were followed up with Phosphoproteomics to identify the kinases and phosphorylated components of the perturbed pathways. In silico approaches revealed perturbations in extracellular matrix remodeling and associated cascades. To assess the extent of influence of Integrin and PI3K-Akt pathways, we used an Integrin Linked Kinase inhibitor on patient-derived meningioma cell line and performed a transcriptomic analysis of the components. Furthermore, we designed a Targeted proteomics assay which to the best of our knowledge for very first-time enables identification of peptides from 54 meningioma patients via SRM assay to validate the key proteins emerging from our study. This resulted in the identification of peptides from CLIC1, ES8L2, and AHNK many of which are receptors and kinases and are difficult to be characterized using conventional approaches. Furthermore, we were also able to monitor transitions for proteins like NEK9 and CKAP4 which have been reported to be associated with meningioma pathobiology. We believe, this study can aid in designing peptide-based validation assays for meningioma patients as well as IHC studies for clinical applications.

High Copy-Number Variation Burdens in Cranial Meningiomas From Patients With Diverse Clinical Phenotypes Characterized by Hot Genomic Structure Changes

Meningiomas, as the most common primary tumor of the central nervous system, are known to harbor genomic aberrations that associate with clinical phenotypes. Here we performed genome-wide genotyping for cranial meningiomas in 383 Chinese patients and identified 9,821 copy-number variations (CNVs). Particularly, patients with diverse clinical features had distinct tumor CNV profiles. CNV burdens were greater in high-grade (WHO grade II and III) samples, recurrent lesions, large tumors (diameter >4.3 cm), and those collected from male patients. Nevertheless, the level of CNV burden did not relate to tumor locations, peritumoral brain edema, bone invasion, or multiple lesions. Overall, the most common tumor CNVs were the copy-number gain (CNG) at 22q11.1 and the copy-number losses (CNLs) at 22q13.2, 14q11.2, 1p34.3, and 1p31.3. Recurrent lesions were featured by the CNLs at 1p31.3, 6q22.31, 9p21.3, and 11p12, and high-grade samples had more CNVs at 4q13.3 and 6q22.31. Meanwhile, large tumors were more likely to have the CNVs at 1p31.3 and 1p34.3. Additionally, recurrence prediction indicated the CNLs at 4p16.3 (p = 0.009, hazard ratio = 5.69) and 10p11.22 (p = 0.037, hazard ratio = 4.53) were candidate independent risk factors.

Pediatric meningioma: a clinicopathologic and molecular study with potential grading implications

Meningiomas are common in adults (~35% of brain tumors) but rare in children, where they exhibit unique clinical, pathological and molecular features compared to adult counterparts. Thus, data generated from adult cohorts may be imperfectly suited to guiding diagnostic, prognostic and treatment decisions for children. We studied 50 meningioma patients ≤18 years with available clinical and pathological data to address the need for data obtained in the pediatric setting. As previously described, we noted a slight bias toward male patients and a higher proportion of spinal tumors compared to adults. Thirty-eight of 50 specimens were further analyzed by next generation sequencing. Loss-of-function mutations in NF2 and chromosome 22 losses were common, but pathogenic variants in other genes (SMARCB1, FUBP1, BRAF, TERT promoter, CHEK2, SMAD and GATA3) were identified in a minority of cases. Copy number variants outside of chromosomes 22 and 1 were infrequent. H3K27 hypomethylation, a useful biomarker in adult tumors, was not found in our cohort. In exploring the correlation between mitotic count and recurrence-free survival, we found a threshold of six mitoses per 10 high powered fields as the optimal cutoff in predicting recurrence-free survival. If independently validated in larger studies, adjusted grading thresholds could enhance the clinical management of pediatric meningiomas.

Molecular Advances in Central Nervous System Mesenchymal Tumors

Mesenchymal tumors of the central nervous system (CNS) comprise an array of neoplasms that may arise from or secondarily affect the CNS and its immediate surroundings. This review focuses on meningiomas and solitary fibrous tumors, the most common primary CNS mesenchymal tumors, and discusses recent advances in unveiling the molecular landscapes of these neoplasms. An effort is made to underscore those molecular findings most relevant to tumor diagnostics and prognostication from a practical perspective. As molecular techniques become more readily used at the clinical level, such alterations may strengthen formal grading schemes and lend themselves to treatment with targeted therapies.